AuthorTopic: OTW Vanguard help (Read 81223 times)

thegrimreaper

Ok guys am thinking of getting an OTW Vanguard with the proper drive, in December Been in touch with Bob and he sounds like a great guy. With all the bits and pieces I have collected over my modeling years I seem to have parts to fit out a WTC for the above sub barring a leveler and speed control, and can`t see th logic in me buying a WTC as all I need is tube end plates and tech racks for the inside would any of you guys who have built the Vanguard possibly supply me with the dimentions of the WTC you are using so I can attempt to make my own

You'll get a first class boat off Bob D. You've seen Jim Hughes boat of course, at the last Dive-in, but that uses the OTW dive module. Paul Holman scratchbuilt a WTC for his OTW Vanguard, based on a water pump ballast system and an 80mm WTC. He used to post on here now and again, but I haven't seen him on here for an ice age.

If you want to keep the WTC below the waterline in order to minimise the size of the ballast tank, then the maximum diameter you can use is 100mm in the Vanguard. You will need to displace about 750-850ml in order to reach a scale waterline- lots of freeboard on this beast.

Hi MarkI built mine with a OTW tank but had a few issues.....I couldn't put batteries under it as the diameter of the WTC was such that they would not fit and used a lead acid up front, similar to the old Ohio and Trafalgar of Sheerlines. This gave immense headaches with trimming but got there in the end. The only issue now is when the water temperature changes from that trimmed at, means it goes out of trim, if that make sense! If I was to do the job again I'd go for a smaller diameter than the standard OTW tube though longer to keep the capacity the same. This would allow the tank to go higher in the hull to get a stick of batteries under the center of gravity/bouyancy. The hull has plenty of room to manouver! My WTC is 110mm diameter - the water tank is 220mm long internaly. Water slop is an issue as well - I have web's in mine that work to a degree but if I was building my own I'd have fitted fuel tank foam that is used on aircraft tanks - bue stuff with loads of largish holes. I work at Duxford so can probably get a source address if you need one. Also I have found the hull upper traps air - I put grill over the holes in my hull to make them look kind of real..... but the water tension knocked that idea into a cocked hat unless you use mesh with larger holes! The OTW hull is great though and Bob's propulsor is very efficient too - I compared it with a similar one fromProp Shop that has fewer blades and it not as good, so I stuck with the OTW version. I still have the Prop Shop one as it is too good to look at to send back!! I do like the Vanguard shape and it is my first nuke - I did a Robbe U47 many years ago but sold that - and for a first go at a proper pumped water WTC type it was a good one due to it's size. If I cane be of helpwith photo's of mine let me know!RegardsJim

If the module had been 100mm instead of 110mm, then the tank could pretty much be halved in volume. A shorter tank is helpful if you're using a system with an exposed water surface like OTW or Sheerline. You'll also benefit from quicker dive times, and use less energy pumping water. I haven't seen anyone try foam baffling before, would be interesting to see if that worked in a model- won't it limit the volume somewhat?

A tip I was given regarding baffling tanks was instead of vertical baffles, install a horizontal one from front to rear at point where the tank would be full. Drill a couple of small holes to allow the air through as the tank is filled.

If you want to sling the batteries underneath the module, you will need to go for 80mm diameter tubing, as even with 100mm there will be insufficient clearance unless you're using pencells! The other option open to you is to install the batteries inside the tube, either a single pack forward of the ballast tank, or twin packs forward and aft.

thegrimreaper

Andy you lost me their I thought that if I used 100mm or 80mm tube for the ballast tank then it would have to be longer to to hold the same amount of water that 110mm, hhmmm horizontal baffle worth experimenting with looks like its going to be 80mm then to get a battery pack in but I also like the idea of the battery inside the module front and rear

would the batteries not be heavier when they were charged ? you are after all putting a charge into them????? sorry sorry

seriously Andy if I was to use 80mm tubbing for the ballast tank how would I work out how big/small it needed to be ?

Regards Mark

Logged

thegrimreaper

Jim, it`s all your fault I saw your Vanguard at the last dive-in and knew I needed to have one have spoken to bob and after watching a u-tube video of a Vanguard with an ordinary prop have decided to spend the extra on the proper thing off Bob. I am looking to put my battery`s either under the module or a battery pack front and rear (Andy Subcultures idea). To prevent air bubbles under the hull top I use a bottle of washing up liquid watered down and spray my Akula to break water tension.If you have any photo`s of your build Jim then I would love o have a look at them also if you had any problems while building that I should look out for any tips whatsoever I would be greatful for

If your wtc is 110mm, in a Vanguard it will project above the waterline when on the surface.

That means you will need a bigger tank, as you will have to displace that volume to submerge the boat. Jim's tank is about 1500ml capacity.

With 100mm diameter tubing or less, with the boat surfaced, all of the cylinder will be underwater, so to submerge, you will only need to displace the volume of the upper hull, sail and appendages, which is about 750-800ml, or thereabouts.

If you're using a pumped pressurized ballast system, which tends to fill about 75% of the tank, for an 80mm cylinder (74mm inside diameter) you would need a tank about 240-250mm long (10"). For a 100mm diameter the tank would be about 150mm (6") long.

You could mix and match, using a central 100mm ballast tank with 80mm cylinders each end housing the batteries and radio gear.

The Vanguard is a long thin hull, with a large flat missile deck. Even a small amount of trapped air will seriously upset trim, as the long hull will provide a greater distance for an air bubble to run up and down. The flat deck makes it easier for air to get trapped, and with a small scale of 1/100th, vents tend to be a bit on the small side.

You could make a couple of the missile hatches hinged, so that any trapped air in the casing pushes them open as the boat submerges. With a couple of those open, you effectively have a huge vent in your hull. Small weights glued underside the hatches would help gravity make them self close once the air was expelled.

If you look at subs from say WWII, the decks were full of slots and holes to enable the casing to vent quickly for rapid dive times, which could mean the difference between life and death for the crew.

With modern nukes, dive times are much more relaxed, slots and holes are a source of drag and noise, so are minimized. For models this can present a problem sometimes, as we don't want to wait minutes for our models to submerge, no matter how authentic it may be.

thegrimreaper

next question their is two types of perspex tube i have found is extruded the best way to go ???. If so then my WTC will be 100mm with a wall thickness of 3mm will this be suitable for what I want to do ??

Hi MarkI've attached some photo's that may or not be of use! The foam I mentioned earlier is a very open cell construction that is used to prevent fire in the fuel tanks - cells of around 1mm diameter.... will try and get hold of some to "show and tell" when we all next meet up - probably at St Albans at this rate! It apparently prevents the fuel from escaping rapidly out of ruptured tanks - I'll probably get put right on that by greater mind's than mine! Front end upper hull joint with locating pins.Rear end upper hull joint - slightly angled backwards to make easier removal/fittment. Anchor nut used on the brass bracket for stainless counter sink to hold upp to lower. Pin's along the upper hull fit into logitudenly elonggated holes in lower hull to hold upper to lower rigid.These are the planes control arms - the grey one is for the front planes out of titanium I had laying about, so I thought I'd put it to use! The rear's are the curved ones. The alignment of the virtical and horizontal ones could have been done better by me, with a tad more off set between them as I made them too close and mine would meet in the middle.... which makes making the control arms so they don't fould each other fiddly - my mistake, so build in a few millimeters off set!! Also I'd try and dry fit them before fixing down the rear end of possible or you end up like me, working down a small opening akin to papering the hall through the letter box. For a good guide to building one I used Steve Neill's build thread on "SubCommittee".... clear photo's and invaluable!! Also Paul Cooks, which is on this site somewhere, is another great thread and good photo's!This photo show's the front hull joint with the port side screen that is quite clear in photo's of the real thing. Not sure WHAT they are for but I couldn't resist in making them "funtional" in letting air out/water in!! I used thin plastic card to "fill in" the joint a bit - same at the rear and it tend's to reduce the gap caused when cutting by the thickness of the blade used. I used a razor saw and still had a large gap that was easily fill with the card and then plastic filler - I was pleased with the results after a bit of head scratching!I hope these have helped in some way - it's a great hull and look's good on the water!Cheer'sJim

thegrimreaper

Right got the ball rolling just ordered 2 pieces of 100mm X 3mm X 500mm clear plastic acrylic tube from clear plastic supplies in chesterfield also got hold of a piece of plexiglass 1200mm X 500MM X 6mm for the end caps. I am going to be busy over my weekend off

Good stuff. When you make the saddles for the wtc, it's worth remembering that in order for all the tube to be beneath the surface when the boat is surfaced and sitting at the correct waterline, the tube will need to be sitting almost on the bottom of the hull, no more than 5-6mm of gap.

thegrimreaper

Acrylic tube has arrived today new blade sorted for jigsaw I don`t posses a lathe so the end plates will be cut out with a jigsaw and then shaped and finished with files and paper lots of work but hey I have plenty of time. Brass rod available at my local B&Q so will make a visit in the morning.

Davy1

Spinning the disks in a power drill and sanding down does work. Laborious but that is the way I did it pre-lathe.Make the O ring disk the smaller diameter one as Ramesh and Andy suggest.Bolt all 3 of them them together to test fit them then bond them.